Primary immune response to keyhole limpet haemocyanin following trauma in relation to low plasma glutamine

Abstract

Severe trauma can lead to a compromised immune response, thereby increasing susceptibility to infections. Here we will study to what extent these early changes in the immune status upon trauma affect a primary immune response to keyhole limpet haemocyanin (KLH). Because glutamine is the preferred respiratory substrate for immune competent cells and known to be depleted after trauma, we studied the immune status and the primary sensitization in relation to the glutamine plasma concentration in a group of severe trauma patients [injury severity score (ISS) >17]. Trauma patients (n = 31) were sensitized with KLH within 12 h after trauma; plasma glutamine concentrations and immune parameters were determined, after which KLH-specific immune responsiveness was evaluated on days 9 and 14. Low plasma glutamine concentrations were found after trauma. Significantly elevated numbers of granulocytes and CD14-positive leucocytes were found, whereas the HLA-DR expression on CD14-positive cells was significantly lower in trauma patients than in healthy controls. Trauma did not change the in vitro proliferative capacity of lymphocytes when cultured with glutamine; however, when lymphocytes were cultured without glutamine, trauma resulted in lower proliferation than healthy controls. Phytohaemagglutinin-(PHA)-induced interferon (IFN)-gamma and interleukin (IL)-10 production was significantly lower after trauma, whereas IL-4 production was not affected. KLH sensitization following trauma resulted in poor skin test reactivity and low in vitro KLH-induced lymphocyte proliferation compared to controls. In contrast, the development of anti-KLH IgM, IgG, IgA, IgG1, IgG2, IgG3 and IgG4 production on days 9 and 14 following trauma was not different from that in healthy controls. Major trauma was associated with a reduced cell-mediated immune response, correlating with low plasma glutamine concentrations, while no effects of trauma were found on the development of a primary humoral immune response.

Fig. 1

Plasma glutamine concentrations. Horizontal bars and boxes show median levels and interquartile range, respectively. Outlier values are indicated as circles. Glutamine concentrations are significantly different (P < 0·001) between the trauma patients versus healthy controls on day 1.

Fig. 2

Cytokine production in supernatant of stimulated PBMCs (10 µg PHA/ml) on day 1 after trauma and of healthy controls. The in vitro productions of IFN-γ (a), IL-10 (b) and IL-4 (c) are expressed in pg/ml. Horizontal bars and boxes show median levels and interquartile range, respectively. Outlier values are indicated as circles. Significant differences (P < 0·05) between the trauma patients versus healthy controls are indicated by an asterisk (anova, Student's t-test).

Fig. 3

In vivo cellular immune responses to KLH on day 14 by means of delayed-type hypersensitivity skin testing. The induration of the skin is shown, as measured 24 h after intradermal injection with 1 or 10 µg KLH.

Fig. 4

In vitro cellular immune response to KLH on day 14; the stimulation indices of PBMCs of trauma patients and healthy controls after 6 days of in vitro stimulation with 15 or 50 µg KLH/ml are shown. Median values and significant differences (P < 0·05) (Mann–Whitney U-test) between trauma patients versus healthy controls are indicated.

Fig. 5

Humoral immune responses to KLH. IgM, IgA, IgG and the IgG-subclasses, IgG1, IgG2, IgG3 and IgG4 specific antibodies to KLH are expressed in arbitrary units per ml serum on days 1, 9 and 14. Horizontal bars and boxes show median antibody levels and interquartile range, respectively. Outlier values are indicated as a circle if present per group of values. No significant differences were measured (GLM repeated measures, factorial).